9.9.7
Flood management
Managing floods reduces damage, but not all countries have the resources. Nations with flood-prevention infrastructure are better at reducing risks.
SkillBuilder discussion Concluding and decision-making, Communicating 1. What is the dam’s role in flood control and water management? 2. How does releasing dam water affect nearby areas? 3. Why monitor dam water levels during heavy rainfall?
FIGURE9 Lake Wivenhoe, Queensland, at 190 per cent capacity, January 2011
FIGURE10 Wivenhoe Dam levels, 2011 and 2022
SkillBuilder discussion Communicating 1. What years are being compared for Wivenhoe Dam levels in the graph? 2. During which year did the dam reach its highest level? 3. What was the approximate percentage of dam capacity on 7/01/2011?
Wivenhoe dam levels Comparing June 2010 to June 2011 and 2021/2022.
200
150
2010/2011
7/04
100
76.3%
50
0
1/06
10/07 18/08 26/09 4/11 13/12 21/01
1/03 9/04 18/05
2010/2011
2021/2022
Source: ABC News and Seqwater
Floods are commonly managed by building barriers like levees (see FIGURE11 ), weirs and dams. Flood control dams must stay below a set level to hold extra water. After 1974 (see FIGURE9 ), Wivenhoe Dam was built, but its effectiveness during the 2010–11 floods was debated. Engineers had to avoid overflow, which could erode the dam wall. Releasing water through the spillway worsened the flood. FIGURE10 compares Wivenhoe Dam levels in 2011 and 2022 floods; although fuller in 2011, water levels rose faster in 2022.
TOPIC9 Water in the world 305
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